Lecture 5: Basic Population Dynamics

CE 107: Introduction to Civil and Environmental Engineering

Population Density

The Demographic Divide: Developed and Developing Nations

• A. Rich Nations 1. Decreased birth rates 2. Low to negative growth rates 3. Increased consumption rates per person 4. Negative environmental impact due not to numbers but affluence. 5. Consequences of affluence a. Greater contribution per person to global pollutants carbon dioxide, ozone depletion chemicals b. Food consumption high on biomass pyramid fewer people can be supported c. Waste production high fuel inefficient transportation, throwaway consumer goods.

Developed and Developing countries

• B. Poor Nations 1. Moderate birth rates (these rates have decreased in the last 20 years) 2. Moderate to high growth rates 3. Low consumption rates per person 4. Negative environmental impact due to numbers not affluence 5. Consequences of population size a. Subdividing farms and intensifying cultivation b. Opening up new lands for agriculture c. Migration to cities d. Illicit activities e. Emigration and immigration f. Impoverishment of women and children

Developed and Developing countries

Fig. Developing countries represent a larger and larger share of world population because of higher populations and higher birth rates.

Population Explosion A. Current world population: 6 billion people (October 1999)

B. Putting the numbers in perspective:

• Each time your heart beats, 3 more people are added to the world

• Each time a person dies, 2.8 babies are born Every day a quarter of a million are added.

• Every year, about 87 million people (about the population of Mexico, or 3x the population of California, or the combined populations of the Philippines and South Korea) are added to the world.

• During the next 2.5 years, the equivalent of the U.S. population will be added to the planet.

• During the coming decade the increased population of one billion people is the equivalent of adding an extra China to the world's population

C. Causes of population growth:

a. Better recruitment resulted from declining infant mortality rates

b. Mortality rates decline:

· Improvement in agriculture increased production and better food

distribution and storage

· Public health measures improved sanitation practices, clean drinking water, mass inoculations

World Population: The Reality

Fig. For most of human history, population grew slowly, but in modern times it has suddenly "exploded. World population started a rapid growth phase in the early 1800s and has grown sixfold in the last 200 years. It continues to grow by nearly 88 million people per year ”

World Population: The Reality and Projections

World population (millions)

# Top ten most

populous countries

1990 2008 2025*

1 China 1,141 1,333 1,458

2 India 849 1,140 1,398

3 US 250 304 352

4 Indonesia 178 228 273

5 Brazil 150 192 223

6 Pakistan 108 166 226

7 Bangladesh 116 160 198

8 Nigeria 94 151 208

9 Russia 148 142 137

10 Japan 124 128 126

World total 5,265 6,688 8,004

World Population growth

First Billion All of Human History (1800)

2nd Billion 123 Years

3rd Billion 33 Years (1960)

4th Billion 14 Years (1974)

5th Billion 13 Years (1987)

6th Billion 12 Years (1999)

7th Billion 14 Years (2013)

8th Billion 15 Years (2028)

9th Billion 26 Years (2054)

Carrying capacity of the Earth environment

• Definition: A concept related to sustainability which is usually defined as the maximum number of individuals of a species that can be sustained by an environment without decreasing the capacity of the environment to sustain that same amount in the future.

• What is the maximum number of people that Earth can sustain?

How many people can Earth Support?

May vary from 2.5 billion to 40 billion.

2.5 bill: if everybody eat like Americans

40 bill: if all flat lands are cultivated

Factors need to be considered

• Food supply

– Support 6 billion if vegetarian. Agriculture production is not increasing much since 1984.

• Land and Soil Resources

– Almost all usable land areas for agriculture used. 13% increase is possible, but extremely costly.

• Water Resources

– Consumption ~ 1000 liters/day, rural ~ 5 liters/day. Only 1% freshwater is available for effective human use

• Net primary productions

– Human uses 4% of land and 2% of oceans production. Since 1950, NPP of the planet decreased by around 13%.

• Population density

– Bangladesh has 915 people /km2

• Technology

– 1 American = 35 Indian = 140 Bangladeshi (??)

Population and Consumption

The “ecological footprint” • The environmental impact of a person or population - Amount of biologically productive land + water - For resources and to dispose/recycle waste • Overshoot: humans have surpassed the Earth’s capacity to

support us Ecological footprints are not all equal • The ecological footprints of countries vary greatly. - The U.S. footprint is much greater than the world’s average. - Developing countries have much smaller footprints than

developed countries.

Population and Consumption

Your Footprint : Example ..food

• Vegetarian: Food footprint 0.2 hectares • Eat meat now and then: Food footprint 0.6 hectares • Eat meat a few times a week: Food footprint 1.3 hectares • Eat meat most days: Food footprint 2.1 hectares • Eat meat once or twice a day: Food footprint 2.8 hectares • Eat meat almost every meal: Food footprint 3.5 hectares

We are increasing the burden on our planet

• • Human population growth amplifies all environmental problems - The growth rate has slowed, but we still add over 200,000 people to the planet each day.

• • Our consumption of resources has risen even faster. – - Life has become more pleasant for us so far.

– - However, rising consumption increases the demands we make on our environment.

– - The rise in affluence has not been equal. The gap between rich and poor has doubled in the past 40 years.

Consequences of a Population Explosion in Developing Countries

Fig. The diagram shows the numerous connections between unchecked population growth and social and environmental problems.

The Demographic Transition

1. Epidemiologic transition a. Pattern of change in mortality factors b. Decline in death rates 2. Fertility transition a. Pattern of change in crude birth rates b. Decline in birth rates worldwide 3. Phases of demographic transition a. The demographic transition is a description of the correlation observed in developed countries between economic development and decreased fertility rates. There may be other, equally effective means of reducing fertility rates.

The Demographic Transition

The Demographic Transition

Fig. 7.8 In developed countries, the decrease in birth rates proceeded soon after and along with

the decrease in death rates, so very rapid population growth never occurred.

The Demographic Transition

Fig. 7.8b In developing countries, both birth and death rates remained high until the mid 1900s. Then

a steep decline in death rates was caused by the rapid introduction of modern medicine, whereas birth

rates remained high, causing very rapid population growth.

Age Structure

• The proportion of the population in each age class. Age structure provide insight into a population’s history.

• The age structure of a population affect current and future birth rates, death rates; and growth rates.

• Rapidly growing nation has shape like pyramids.

• In developing country 37% population are under 15.

• Slow growing nation has eye shape.

Age Structure

Age Structure

Projected Future Trends

Fig. This figure shows projected world population according to three different fertility scenarios. UN projections of the future world population, using different total fertility rates.

Reality of the problem

Fig. Poverty, environmental degradation, and high fertility rates become locked in a self-perpetuating

vicious cycle.

Population Impact on the Environment

Environmental Impact (EI)

= Population (P)

X Per Capita Resource Consumption (A)

X Technological Impact (T)

Population (P) Affluence (A) Technology (T)

Environmental Impact

Number of people

Number of units of resources used

per person

Environmental degradation and pollution per unit of resource used

Environmental Impact of

Population